Apparatus for thermally processing of continuous lengths of fibrous materials

ABSTRACT

An improved apparatus is provided for the thermal treatment of continuous lengths of fibrous materials (e.g. drawing, relaxing, drying, etc.) which comprises an elongated heat treatment tube enclosed in a coaxial cylindrical jacket. A heating element may be positioned within the annular space that surrounds the heat treatment tube to impart heat to a fluid introduced into the annular space at the inlet end of the apparatus. This heated fluid may then be directed both to an aspirator at the inlet end of the heat treatment tube and to a gas port which communicates with the inlet end of the apparatus. Valve means are provided for closing the gas port at the start-up of operations to permit the aspirated gas to pull the end of the fibrous material through the heat treatment tube. After start-up the gas port is reopened and the fibrous material preheated before it enters the heat treatment tube. The fibrous material also is heated by radiation from the wall of the heat treatment tube. Optionally, the exit end of the apparatus can be provided with means to recycle a portion of the fluid. The apparatus is particularly suited for the thermal treatment (e.g. hot drawing) of a continuous length of a multifilament polybenzimidazole fibrous material.

United States Patent [191 Ferment et a1.

[ APPARATUS FOR THERMALLY PROCESSING OF CONTINUOUS LENGTHS' OF FIBROUS MATERIALS [75] Inventors: George R. Ferment, Dover; Stuart M. French, Chatham, both of N..l.; Paul A. Sessa, Charlotte, NC.

[73] Assignce: Celanese Corporation, New York,

22 Filed: limits 1,1974

[21] Appl. No.: 438,303

[52] US. Cl. 219/388; 28/61; 34/155;

68/5 D; 219/365; 264/290 R; 264/345 [51] Int. Cl. F271) 9/06 [58] Field of Search 28/61, 62; 219/365, 388,

' 219/400; 260/784; 264/288, 290, 345; 34/155; 57/34 HS; 68/5 D, DIG. l

2/1959 Switzerland 219/388 1 May 13, 1975 581,097 8/1958 Italy 219/388 Primary Examiner-Vobdymyr Y. Mayewsky [57] ABSTRACT An Improved apparatus is-provlded for the thermal treatment of continuous lengths of fibrous materials (e.g. drawing, relaxing, drying, etc.) which comprises .heat treatment tube to impart heat to a fluid introduced into the annular space at the inlet end of the apparatus. This heated fluid may then be directed both to an aspirator at the inlet end of the heat treatntent tube and to a gas port which communicates with the inlet end of the apparatus. Valve means are provided for closing the gas port at the start-up of operations to permit the aspirated gas to pull the end of the fibrous material through the heat treatment tubc. After start-up the gas port is reopened and the fibrous material preheated before it enters the heat treatment tube. The fibrous material also is heated by radiation from the wall of the heat treatment tube. Optionally, the exit end of the apparatus can be provided with means to recycle a portion of the fluid. The apparatus is particularly suited for the thermal treatment (e.g. hot drawing) of a continuous length of a multifilament polybenzimidazole fibrous material.

7 Claims, 10 Drawing Figures PATENIED M I 31975 SHEET 10F mm m l m I////.////// f/////\///// 1 I 2 APPARATUS FOR THERMALLY PROCESSING'OF As setforth in US. Pat. No: Re. 26,065, the aromatic CONTINUOUS LENGTHS OF FIBROUS polybenzimidazoles having the recurring units of For- MATERIALS mula ll maybe prepared by self-condensing a trifunc- BACKGROUND OFcrHE INVENTION tional aromatic compound containing only a single set p 7 g 5 ofortho, disposed diamino substituents and an aro- I A variety of apparatusand processes have been proma'tic,' p'referably phenyl, carboxylate ester substituent. posedin the past for thethermal processing ofacontin- Exemplary of polymers of this type is poly-25( uous length of fibrous material on a'continuous basis. benzimidazole prepared by the autocondensation of For instance, a continuous length of synthetic; polyphenyl-3,4-diaminobenioate. mel'ic material -8 p y m zo e fib ou mater 10 As also set forth in the above mentioned patent, the rial) m y b r w r lax Q lh lw y aromatic polybenzimidazoles having the recurring units "flied Passing u h I g'fmm of an of Formula I may be prepared by condensing an aro- PP P Q aPPaYatUS. 1 g matie tetraamine-compound containing a pair of or- POIYbWZlmldaZOM are knowncla 0f helflocyclic thodiamino substituents on the aromatic nucleus with polymers. Typical polymers of this class and their prepa dicarboxyl compound selected from the class consistaration are more fully described in US. Pat. No. ing of (a) the dipheriyl ester of an aromatic dicarbox- 2,895,948, US. Pat. No. Re. 26,065, and in the Journal ylicaeid, (b) the diphenyl ester of a heterocyclic dicarof Polymer Science, Vol.50, pages Sl l-539 (196i) boxylic acid wherein the carboxyl groups are substituwhich are herein incorporatedby referenee. The polyvents upon a carbon in a ring compound selected from benzimidazoles consist essentially of recurring units of the=class consisting of pyridine, pyrazine, furan, quinothe following Formulas l-and ll. Formula I is: live, thiophene and pyran and .(c) an anhydride of an aromatic dicarboxylic acid.

. N V 1 Examples of polybenzimidazoles which have the re- 5 curring structure fof, Formula I are as follows: R C poly-2,2'-(m-phenylene )-5 ,5 '-bibenzimidazole;

v poly-2,2'-(pyri dylene-3",5'')-5,5-bibenzimidazole;

I poly-2,2'-(furylene-2",5")-5,5'-bibenzimidazole; H H poly-2,2-( naphthalene-l ",6" )-5,5

bibenzimidazole;

poly-2,2'-(bipheiiylene-4'f,4") S,5'-

wherein R is a tetravalent aromatic nucleus, preferably bibenzimidazole; symmetrically substituted, with'the nitrogen atoms poly-2,2-amylene-5,5'-bibenzimidazole; forming the benzimidazole rings being paired upon adpoly-2,2'-oetamethylene-5,5'-bibenzimidazole; jacent carbon atoms, i.e., orthocarbon atoms, of the poly-2, 6-(m-phenylene)-diimidazobenzene; aromatic nucleus, and R is a member of the class'conpoly-2,2'-cyclohexeneyl-5,5bibenzimidazole; sisting of I) an aromatic ring, 2) an alkylene group poly-2,2'-(m-phenylene)-5,5 -di(benzimidazole) (preferably those having four to eight carbon atoms), ether; and (3) a heterocyclic ring from the class consisting of poly-2,2'-(m-phenylene)-5,5'-di(benzimidazole) sul- (a) pyridine, (b) pyrazine, (c) furan, (d)"quinoline, (e) 40 fide; thiophene, (f) pyran. poly-2,2'-(m-phenylene)-5,5'-di(benzimidazole). sul- Formula ll is: fone;

poly-2,2'-( m-phenylene )-5 ,5 '-di( benzimidazole) N methane; poly-2 ,2"-(m-phenylene)-S',5"-di(benzimidazole) t -C 2- propane-2,2;and

\ poly-2',2"-(m-phenylene)-5 ',5"-di( benzimidazole) ethylene-l ,2 where the double bonds of the ethylene groups are intact in the final polymer.- I The preferred polybenzimidazole for use in the preswherein Z .is an aromatic nucleus having the nitrogen ent invention is one 'prepared from poly-2,2'-(matoms forming'the benzimidazole ring paired upon adphenylene)-5,5,'-bibenzimidazole, the recurring unit of jacent carbon atoms of the aromatic nucleus. which is:

Preferably. o atic po ybenzimidazoles a e se- Any polymerization process known to those skilled in lected, e.g., polymers consistingessentially of the rethe art. may be employed to prepare the polybencurring units of Formulas l and II wherein R is an arozimidazole which may then be formed into a continumatic ring of a heterocyclic ring. ous length of fibrous material. Representative techniques for preparing the-polybenzimidazole are dis ence.

andd dicarboxyl compound are introducedjntoa first stage melt polymerization reactionj "zone, andheated therein at a temperature aboveabout-200C., preferably at least 250C.,fand-mo re" preferably from about. 270to 300C. The reaction .is'conductedina ,substantially oxygen-free atmosphere, i.e'.,"below' about 20' ppm oxygen and preferably below about18 ppm oxygen,

until a foamed prepolymer is formedhaving' an inhera j ent viscosity, expressed as deciliters'per gramsof-at, least 0. l and preferably from about 0,1 3 to 0.3, the inL-j herent viscosity (l.V;) as used herein psirig'j eiemine from a solution of 0.4 grams of thepolymerin 100mb" of 97 percent i-LSO, at ZSf'CIf 1-.

After the conclusion of thefirststag'e reaction,

normally takes at least 0.5 hour and preferably l toj 3 hours, the foamed prepoiymer is co'oled and then pow: dered or pulverized in any'conveni'ent rnanner. The resultlngiprepolymer powder is thenintroduced into a seconcl'stage polymerization reaction zonewhereinit is heated under substantially 'oxy'gen-free'conditjons as described above, to yield a polybenzimidazole polymci' product, desirably having an l.V., as measured above,

of at least 0.6, e.g., 0.80 to M or more; The temperature employed in the second stage is at least 250C., preferably 'at least 325C.-, and morepreferably from about 350to 425C. The second stage reaction generally takes at least 05 hour, and preferably-'5' from about-l to 4 hours or more. i I

A particularly preferred method: for preparing the to yield the finalproduct.

As is known in theart, po'lybenzirriida'zoles are getter-- ally formed into continuous lengths'of fibrous'materials by solution spinning, thatis, by dryor wet spinning'a solution of the polymerrin an appropriate solvent such as N,N-dimethylacetamide', N,N di methylformamide,

(w on y; in we! spinning) ihroughan cachin -predetermined shape'-l 1 tk l 1 h art-ma bqs ls -a dimethylsulfoxide. or 'sulfuricacid into an evaporative atmosphere fotthe solventin which most of the solvent isevaporated (dry) or into'a coagulation bath (wet), resulting'in thepolyri erhavingthedesired filamentaryshape; I

The polymer solutionsflrnaybej-'accordance with known procedures. For example, sufficient polybenzimidazole may. be dissolved in the solvent to yield a final solution suitable for extrusion containing from about l0 to 45 percentby weight of the polymer,

based on the total weight of thei'solution. preferably from about 20 to 30percent by weight.

One suitable means for dissolving the polymer in the solvent is by mixing the materials at a temperature above the atmospheric boiling point of the solvent, for example 25to l20C. above such boiling point, and at a pressure of 2 to 15 atmospheres fora periodof l to:

5 hours.

With respectto aromatic polybe'rt zimidazoles,prefer ably equimolar quantities of the monomeric tetraamine Preferably the' polymer solutions, after suitable filclosed In US. Pat. Nos. .3,509,l08,.3,549,,603, and r 3,55l,389, which are assigned to the'assignee of the present invention and are herein incorporated by refertration'to remove any undis'solved portions, are dry spunL For example, the' solutions may be extruded throughaspinneret into aconventional type downdraft spinning column containing a-circulating inert gas such asnitrogen noble gases, combustion gases or superlheated steam. Conveniently,- the spinneret face isat a temperatureofjfrom about l00to l70C., the top of thecolumn fr'omfabout l20to 220C., the' middle of 10 the columnfrom about l'40to 250C, and the bottom of the column frorn'fabout i60to 320C. After leaving the spinninglcolummthe continuousfilam'entary materials. are.talten up, for"ex'am'ple, ata speed within the (range of about! to meters or more per minute. if 'th'e",continuousfilamentary materials are to, be washed g while w'o und g on bobbins,.- the resulting ,as- I spunl' lr 'riaterials mayif be subjected to a' slightsteam drawing treatment ata'draw ratio of from about l.05:l "Y to l 5;l in'orderto preventtheiibe'rs fromrelaxing and '{falling off {the bobbin during, the subsequent washing step; Further-details :ivith "respect to a method for d spinning iaxcontinuous length of a-polybenzimidazole fibrous material are shoivn -in U S;1Pat. No. 3,502,576

to Bohrer'et al. which is assigned to the same assignee as the present invention and is herein incorporated by rf,rence'.

The continuous length of polybenzimidazolefibrous material'isnext washed soi-as to remove at least the major, portion of residual spinning solvent, e.g'., so that the washed materials'contain less than about i percent by-weight solvent basedon the'weight of the continuousfilamentary material, and preferably soas to'obtain an fessentiallyspirtning solvent-free fibrous material (i.e.-, a fibrous material eont'aining less'thanabout0.l

percentjsolvent-by weight). Typically, a simple v water wash is employed; however, if desired, other wash -r naterials such asacetone, methanol, methylethyl ketone and similar solvent-miscible and volatile organic solventsmay be used place of or in combination with the'water. The washing operation may be conducted by collecting the polybenzimidazole fibrous'material on perforated rolls orbobbins',Simmersingthe rolls in the liquid washbathfand pressurewashin'gthe fibrous material,'for example, ffor'about 2 to-'4 8'h'ours or more. Alternatively, the continuous length 'of polybenzimid'a'z'ole fibrous materialm'ay be washed ona continuous basis by. passing' theltibrous material in the direc- .tion ma gamuirpugnbn j r more liquid wash baths ('e.g., for l'toa 10 minutes), Any wash technique known 7 The ohtinuous'lengthof polybenzimidazolefibrous 'materi'alf ma y next be dried,to "remove-the liquid wash bath by any; convenient technique.- Forinstance, the drying opeia tionfqr bobbins ofyarn maybe conducted at a temperatufegfofabout' 15010 30013,- for about 2 to l00-- hours 'orj-moi'e; Alternatively, Ithe continuous As is'known to those skilled in polybenzimidazolefiber 'technology,- the' fibrous' material ha's'a propensity to v'pick'-up-about. l0 to*'l3"percent mo'isture by weight when exposed to ambient conditions foran appreciable period of time. 3

5 of continuous lengthsof fibrous materials on a continu- Heretofore continuous lengths of; polybenaimidaz ole fibrous materials have been hot drawn (1 ).while in sliding contact witha hot surface."e.g. a hot shoe. or (2) while passing fora plurality of passesthrough a radiantly heated drawing zone inwhich the fibrous material is suspended. Difficulties-have been encountered with hot shoe polybenzimidaz ole drawing techniques be perature maintenance uniformity has been of prime lmportance. When radiant heat has been supplied to the polybenzimidazole fibrous,material in, priorart tech-J ous basis wherein the initial stringup of the fibrous materiai. is rendered simple.

: -These and other objects, as well as the scope, nature, and' util ization of-the process will be apparent from the following detailed description and'appended claims.

. f "swarm-0pm lNVENTlON j fi been foundthat in an apparatus for thermally niques (e.g., the process oi' U si PathNo. 3,622,669

it has been essential that the continuous-length ot fi brous material be passed through the drawing zone for a plurality of passes in order to accomplish the desired degree of drawing. Such processesadditionally require a complex string-up arrangement'which'is impractical for large scale economic production,and commonly are accompanied by the production of .brokenffilaments.

ln commonly assigned US. Pat. application Ser. No. 297.511 filed Oct.

process for drawing continuouslengths of 'polybenzimidazole filaments and an improved apparatus for carrying out the process. a

l3, l972,- now U.S.,-Pat. No.. 3,849,529, of G. R. Ferment, A. E. Prince, Jr., and P. A. Sessa there are disclosed an improved-single. pass Essentially, the apparatus disclosed'in the copending v application comprises an elongateddraw tube which'is surrounded by a coaxial, cylindrical heating :jacket.

Provision is also made for introducing'a heated gas di rectly into the draw tube. This arrangement permits heating the filament both by radiant'heat through'the.

wall of the draw tube and byv direct 'contactwith the 40 iinlet' e nd andan outlet endzto take up means, an imheated gas. The present invention is considered an advance over the subject matter or] U.S. Pat. application Ser. No. 297,51l.Theprocess,of.U;S. Pat. application 1 Ser. No. 297,51 1 is improved when the process modifications disclosed herein are adopted, and the improve apparatus disclosed herein utilized.

It is an object of thepresent inventionito provide animproved apparatus and process for'the'thermal pro-, cessing (e.g. drawing, drying; relaxing; etc.) of a wide variety of continuous lengths of fibrous materials on a continuous basis. i

It is an object of the present invention to providean improved apparatus and process which is particularly suited for the hot drawing of a polybenzimidazole fibrous material. Y

it is an object of thepresent invention to provide an improved apparatus and processjwhich,respresents'an advance over the subject matterof commonly assigned US. Pat. application Ser., No. 297.51 I; p

it is an object of the present invention to provide. an improved apparatus for thennally processing continuous lengths of fibrous materials which iscompact-and requires no external heaters.

it is another object of the present invention to provide an improved apparatusfor thermally processing,

continuous lengths or fibrous materialswherein heat loss is minimized and fuelconserved. I

it is a further object of the present invention to provide an improved apparatus for the thermal processing an unprovement.comprisesiproviding:

- anelongated'.cylindrical jacket coaxially surrounding the heattreatrnent tubefo'r providing an annular I chamber aboutthe heat treatment tube; means forintroducing a fluid into the annular chamber; I means operablyx connected to' the heating unit for heatingjthe fluid and promoting the conduction of heat from-the annular chamber through the heat treatment tube; to heat continuous lengths of i"- .brousrnaterials passing therethrough; and means connected to theinlet end-of the heat treatment u ers: introducing heated fluid from the annularxcha'rnber into. the heat treatment tube to .fthereby further heat-.the'continuouslengths of fibrous materials passing through the heat treatment it has been foundfthat 'ina process forthermally treating continuouslengths of fibrous materials including the step of passing the, fibrous materials through an elongated cylindrical heatftreatment tube having an provement comprises:

"introducingfiuid intojan 'annular ehamber coaxially Y 'surroundingthe cylindrical heat treatment .tube',

heatingithc' continuous lengthsof fibrous materials passing through the cylindrical heat treatmenttube hea'ting ,the'fluid and promoting the conduction of I heat i'rom thea nnular chamber through the heat -treatmenttube, and- I introducing heated'fluidfrom the annular chamber directly into theinlet'end of the cylindrical heat treatment tubers; passage through said heat treatment tube along with the-continuous lengths ot fibrous material." I I S asc es O F-THE oaawmos FIG. 1'11; a' schematic representation of an apparatus of the present inventionshowing its relationship to a continuous length-of fibrous material being treated.

FlG."= 2,'consisting.of two parts, is alongitudinal section of the entire, heating unit of the present invention showingthe internal structure, wherein the inlet end is shown-in theupper part of FlG.,2 and exit end is shown in 1 the. lower part'ofFlG. 2.

FIG. 3 is a-transv'erse, section taken on lines 33 of FIG. 2 and shows the structure and arrangement of the preheat means.

FIG. 4 is a transverse section taken on line 4-4 of.

FIG. 2 and showsthe location of the nozzle.

FIG. 5 is a transverse section taken on line 5--5 of FIG. 2 and shows the internal arrangement of the heat treatment tube and the heatingmeansjwithin the annular space about the heat'treatment'tube.

FIG. 6 is-a transverse section taken on line 6-6 of The continuous length of polybenzimidazole fibrous FlG. 2 and shows the entry ports for the heating fluid and the heating means.

FIG. 7 shows an alternate embodiment of the portion of the preheat control unit represented in FIG. 3.

FIG. 8 is a longitudinal sectional view of the exit end of the apparatus showing an alternate embodiment in which means are provided for recycling a portion of the exiting fluid to the incoming fluid.

FIG. 9 is a transverse section taken on line 9-9 of HO. 8 showing the relative location of the bypass means.

FIG. 10 is a longitudinal sectional view of the exit end of the apparatus and shows a further embodiment of means for delivering a portion of the exiting fluid into the incoming fluid.

DESCRIPTION OF PREFERRED EMBODIMENTS The continuous length of fibrous material which is thermally processed in accordance with the present invention may be natural or synthetic in origin. Lengths of fibrous materials consisting of staple or continuous fibers may be processed. The continuous length of fibrous material preferably is formed-of one ormore continuous filaments, and mostpreferably isa multifil-.

per filament of about i to 20, and most preferably about 3 to 16 (e.g.. 3 to 6 for a multifilament tow and 8 to 1.6 for a muitifiiament yarn)..Multifilament yarns selected for use in the process preferablycontain about 10 to 500 filaments, and most preferably about to 200 filaments. A multifiiament towselected'foruse in the processpreferably contains about l,000 to 300,000 filaments, or-more, and most preferably about 50,000 to 150,000 filaments. when tows containing an extremely large number of filaments are drawn in accordance with the present invention, it is preferred that the tows be supplied to the heat treatment tube (described hereafter) while in a flattened ribbon-like configuration.

The fluid introduced into the apparatus of the-present invention is preferably air; however. other gaseous atmospheres such as nitrogen. argon.- helium. superheated steam. etc. may be selected.

The fluid provided in the heat treatment tube is preferably at a temperature of about 400to 600 C" and most preferably at a temperature of about 430to 530C. when hot drawing a continuous length of polybenzimidazole fibrous material.

'ment 'tube 'provided with a flowing fluid as described hereafterwith heat being supplied to the fibrous material both by radiation and-convection. The polybenzimidazole fibrous material may bedrawn at a draw ratio of about 2:1 to 5:l while passing through the heat treatmenttube, and most preferably at a draw ratio of about 2:1 to 3.5:l.

The term "draw ratio," as is well known, is a measure of the degree of stretching during the orientation of the fibrous material, expressed as the ratio of the crosssectional area of the undrawn material to that of the drawn material. While any of the several known ways for; measuring or determining draw ratio may be employed, typically, the draw' ratio is found by taking the ratio of the surface speed of the take-up roll at theexit end of theheat treatment tube to thesurface speed of thefet-d-or'supplysoll atthe entrance end of the heat treatment tube.

.- it is possiblethat the-continuous length of polyben zimidazole-fibrous material which is drawn in the present invention be in intimate association witli a substantial quantity-of water-when introduced into the heat treatment tube (described hereafter), i.e., the fibrous material may be (l).in-intimate'assoeiation with its equilibrium moisture content of about 10 to -l 3 percent weight based upon the weight of the fibrous material, or (2).be soaking wet and contain up to about] 00 percent by-weight' of 'water based upon the weight of vthe fibrous material, e.g., often about 15 to about 70 35. percent by weight of water. When the fibrous material is provided in association with art-appreciable quantity of water the drying'may be surprisingly-conducted sin'iultaneously withdrawing in the heat treatment tube (describedhereafter) without foaming or sacrifice of tensile properties within the resulting drawn fibrous material. Atime consuming separate drying step may accordingly be completely eliminated.

.The minimum hot drawing residence time for a polybenzimidazole fibrous material, i.e., the time during which .the. material is heated while suspended in the heat treatment tube while under a longitudinal tension,

is dependent upon'the single filament denier of the fibrous material, the number of filaments in the continuous length of fibrous materiah'and whether the fibrous material is in a substantially anhydrous form when introduced into th'e'heat treatment tube. These factors also determined the optimum residence times of the fibers' in the-heat treatment zone. Typically, when filaments of about l to 20 denier are present in a yarn of about l0 to 500 filaments, residence times of about 0.05 to l0 seconds,-preferably 0.l to 2 seconds, and more preferably 0.2 to 0.5 seconds are employed.

When processing tows of about 50,000 to l50,000 filaand preferably about. 50 to" I-SO Jmetersper minute.

when processing a multifilament 'yar'n'."

Referring briefly to FIG. 1, it'is'seen that the heating unit comprises essentiallyanyelongatedcylinder ii'idf cated generally by reference numeral 2, through which the continuous length of fibrous'materiai l is passed-in the direction of length"while'taxially suspended therein to take-up means, The "fibrous material ,'is placed under a longitudinaitension byv two pairs of skewed rollers indicated generally by l8 and 19, re-

spectively. The inside of the cylinder is heated by means of an'electrical element, not shown inFlQ. 1, but whose external connections'are"i ndicatedat 5.1 Cras is also admitted tothe inside'of-the cylinder through I inlet port.4,'as will be morefuily described below.

Referring to FiG. 2, which'jconsists of two parts, it will be seen that the fibrous material 1 is passed continuously through elongated heat treatmenttube' 6 which '1 A solid rotatable cylindrical member is inserted in the remaining space of recessed opening 40 of the stationary cylindrical end plug 12. This rotatable cylindrical member bears on surface of the nozzle and also fits tightly within space 40. A central bore 26 is axiaii y coincident with the axis of the heat treatment tube and the bore of the nozzle and is of the same diameter as the nozzle bore 27. A duct 28 is'provided in the body of endplu g l2 which connects the annular space 9 with the matching duct'29 through flange 30 of the nozzle.

-' Duct'2 9, in turn, connectswith duct 31 in the rotatable cylindrical plug member 25. Duct 31 branches into legs defines a heating zone 7. Surrounding the heat treatment tube 6, there is a concentric, coaxial, elongated, cylindrical jacket 3 of sufficient diameter to provide an annular chamber between theheat treatment tube and the inside surface of the cylindrical jacket to accommo- 33 and 34, which'ope n into the central bore 26. Handle 32 secured in any suitable manner to member 25, is used to rotate the latter. As shown in the upper portion of BIG. 2,- ducts 2 8 29, 31, 33 and 34 are in such position that the hot gasesinannuiarspace'9 will be conducted to the central bore'26..The purpose of this arrangement is to preheat the fibrous material as it enters ti; apparatus and tominimize the reception of relatively cooler ambient air into the-nozzle bore 27. During string-up, however, the handle is used to rotate duct '31 out of register with duct 29 so that no fluid can be conducted from annular space 9 tothe inlet end of bore date a heating element 8. This heating'element is a coiled electrical resistance heating element with the ends extending from the exit end of theapparatus connected by means of leads 5 to a sourceofeiectricai energy (not shown). A heat transfer fluid, suchas air, is admitted to .the annular chamber 9 through" gas inlet port 4 in end closure 38. Leads'S are also admitted into the annular chamber through the same end clo'sure3 8.

As can be seen by the arrows, the air inlet port islocated at theexit end of theapparatus. v

Referring specifically to the upper portion of FIG. 2,

it will be seen that the inlet'end of heat treatment tube a 6 is provided with an enlarged shoulder 10 and an extension ll. Extension 11 of heat treatment tube 6 is inserted into a cylindrical opening 39 he stationary eyiindrical end plug 12 which is enclosed in an overhanging extended portion of the cylindrical jacket 3 and is secured to end plug 12 by means ofsetscrew 13. End plug 12 is provided with a duct 14, one end of which communicates with the annular chamber 9, the other end of which connects with a conicalbore 15 to form an aspirator in end plug 12. Stationary cylindrical plug 12 is provided with a cylindrical recess which extends from the extreme left end, as'seen in the upper portion of FIG. 2, and ends as shoulder'4l. A nozzle 16 having an axial bore 27 is secured F shoulder 41 by means of screw 17. Nozzle 16 is of sufficient length to extend into conical bore 15 its entire length. The outside surface of nozzle 16 is also conical in shape and tapers inward toward the end of bore 15 to provide a con-' ical annular space between the inside surface of the conical bore 15 and the outside conical surface 24 of nozzle 16. in a preferred form, the nozzle tapers less rapidly than the conical bore in the end plug with the result that the conical annular space between the plug and the nozzle gradually decreases in width. As a result, the velocity of the fluid passing between the two parts gradually increases to provide an aspiration zone of low pressure as a result of the Venturi effect at the exitend of the nozzle.

26. By-so doing, all-lot the gasis directed through duct l4 around the outside'su'rfaceof nozzle 16. Because of the progressively decreasing diameter of the conical space of aspirator 15 the velocity of the fluid increases until itreaches a maximum at th'e'e xitend of the nozzle.

The space immediately-beyondthe end of the nozzle thus becomes a zone of my low pressure, i.e. an aspiration zone and sen/es to-draw the end of the fibrous material into the apparatusandthrough the heat treatment tube 6 during string-up. Once the end of the fibrous material has beensecuredto take-up means (not shown) the cylindrical member 25 is rotated so that hot gases will be permitted to pass from the annular space 9' into. the inlet end of bore 26 to preheat the fibrous material as it enters the, apparatus. Thus, the fibrous material passing through the heat treatment tube is heated both by the hot gases which surround them dur ing passage through heat treatment tube 6 and also by radiation from the walls of the heat treatment tube which have been heated by the fluid present in annular chamber:9.."

: Rotatable plug 25'is secured in place by means of a sealingring 35 whichis secured to the stationary end plug 12 by means of screws 36. To provide the necessary sealing pressure of the rotatable plug 25 against 'the surface of flange 30 of nozzle 16, a spring loaded washer 37 is ins'ertedbetween ring'35 and rotatable cylindrical member 25'.

Temperature sensing elements 21 and 22 are inserted in bore 26, and the entrance end of heat treatment tube '6, respectively, to measure the temperatures at those points. V

Should additional'or auxiliary heating fluid be dcsired or needed, plug 42a which closes a port leading into duct 14 may be removed and replaced by an inlet tube connected to the same or some other source of fluid.

Referring to the lower portion of FIG. 2, it will be seen that the heat treatment zone of the apparatus comprises that part which extends between the nozzle and, the end closure 38 at the exit end of the heat treatmenttube. This heating area, as already described, may contain heating element 8 wound in a spiral around l l heat treatment tube 6. Air: or other fluid .forced through port 4 in end closure 38 travels through the annular chamber9 and is heated by'the 'electricai heating, 1' element 8. At the same time; beating elernentB irnpa'rts heat to the wallof heat treatmentf tube' ,6 Thus, afrbrous material passing-throughthe draw tubeijf 6 is heaied mb! q flhiili i w 'fjj with theincomingfluid forgreater economy of material through the tube andralso byradiationjfronrthe' heated H walls of the 'tube. A-tenrpcrature 's'erising.device 23, similar to 21 andZ2'isinsertedmearjthe patter-ease the draw tube to 'measure ith'eftemperature bf exit ing gases. These temperature jsensiri'gjJdevices.jeon

nected to measuring instruments (notshown) give the operator the information necessary to control the tem perature at the several criticai points between the en-, 5

trance and the exit ends of thejapparatus. After heating 0 j is completed, the fibrous materialiandtluid'rnay exit through the open end 42 of draw tube 6.

ment described in FlGJZ, theexitigases may be exhausted to the atmosphere. ,-However, 'another preferred embodiment provides for a portion of the gases to be collected and delivered into the entering gases, as

described below. "1.

Referring to FIG. 8, the cylindrical outer jacket 3, in

the just-mentioned preferred embodiment, is extended 4 beyond the exit end 42 of heat treatment tube 6 to fonn a hollow cylindrical chamber beyond theexit end f. m er amqum'pf'fluid w g to the interior "of bore 2 6-isregulated by: turning the screw with a heat treatment tube6. Into this chamber is inserted a chambered cylindrical plug, designatedgenerally as 43,

longitudinal axis of the screw.-Thus, as shown inFlG.

7, the cutout portions ofscrew 60 provide communica- I tion between the annular chamber 9 andv the interior of {and heat. j

end, i.e an annular"restriction. This constriction restricts the axial flow ofjfluidrand causes a certain amountof back'pressurewhich resultsin an additional .flowof fluidthrough the porou's walls of the tube. In this mannen'even: less of the fluid is exhaustedto the atmosphere while'-';an, additional amount is recycled g l-jig;7fdisclosesstili,a .furtherembodiment er the resent invention. 1 embodiment, a preferred "odification is made-armament for preheating the tibroii'sfrnaterial'stme eiitr anc'e'end of the apparatus. ,1 ;Rei't'rring to FICLW, rotatablemember 25, instead of being provided with duct 31 and'branchin'g' ducts 33 and 34, as shown infthe upperportionof FICn'Z, has instead a'hole15 8 drilled'radially from the-"outer surface of therotata'ble plug to the'a'xial bore 26. This hole'is a L thenthreaded to acco'modate screw 60. A duct 59 con- As just described, it was shown-that in the embodinects'dtict 29 inthe flange of thenozzle -with the just described radial threaded hole 58. lhus,' there is again whose outer wall 44 is of such dimension as to fit tightly inside the opening of the extension of cylindrical jacket 3 to form an air-tight sealIThis plug 43 is se'aledfin the opening by any suitable means; Plu'g 43-is provided 5 with an inner cylindrical chamber 45jwhich is shorter than the length of the plug itself. End walls 48 and49 of inner cylindrical chamber 45 have circular holes 46 and 47, respectively, of a diameter smaller than that ofthe inner cylindrical chamber 45. Through these holes is inserted a porous tube 54 which'is the same length as chambered cylindrical plug 43. This porous tub'e has an inner bore 57 of the same diameter as draw tube 6. The chambered cylindrical plug 43'alsohasdrilled in it a gas duct 50 which connects aninletport 51 with the annular chamber 9 inside the cylindrical jacket 3 .-This duct is of unifrom diameter up toa point wherehole 53 through wall 52 of the inner cylindrical chamber 45' connects the latter with duct 50. From that point to where the duct opens into the annular space 9, the diameter constantly increases. The pressure of the exiting gases is sufficient to cause a portion ofthese gases to diffuse through the walls of porous tube 54-intoinner cylindrical chamber 45 and from there to pass through hole 53 into duct 50. There-they minglefwith incoming gases forced in through port 51' and are recirculated through annular chamber 9 through the noz zle and into the heat treatment'tube 6. ln this-mannenless of the gases are exhausted to the. atmosphere, while the gases freshly blown in through port 51 are-preheated. Thus,

there is not only a reduction in exhaust gases in'the atcut-out:portions-6l' and which are paraflel to the screwdriver in slot -.;ACCess to the screw is provided ,by hole 63 which is drilled in the outer cylindrical jacket 3 andhole 64 which is drilled in stationary cyiindricalend plug 12. As shown, the maximum amount of fluid will flow through this combination of ducts. How'- ever, the amount can be decreased by increments by turning the screw one turn clockwise for each increment offlow to be decreased. Thus, by predetermining the pitch ofthe'thread in hole'58 and-of the screw 60, the amount of axial travel can be predetermined for each turn of the screw. As in the case of the embodiment showrijin the upper portion of HO. 2, these ducts can be closed off during stringup by rotating the member 25 by means of handle 32.;By means'of this modification, it is possible'to obtain a more precise control of the amount of preheatingfluidwhichis directed at the incoming fibrous material."

most'preferably a Reynold's number of about 5,000 to ferredembodiments, it is to beiunderstood that variationsand modificationsmay'be resortedtoas will be As previouslyindicated, the preferred embodiments of the apparatus as describedabove are particularly suited for carrying out the polybenzimidazole drawing process-of'U.S.' Pat application Ser. No. 297,5l i. For this purpose the overall length of the apparatus advantageously can be. about-2f tor6 feet. A suitable length to overalljdiameter can'vary frorn about4:l to 10:1. The

bore of theheattreatrnent tube can'be about SH 6 inch inner diameter,and the walls of the porous tube can have athickness ofabout 15 inch or less. The stream of fluid (e.g. air) can be introduced at a rate to produce a gas flow in the main bore of the heat treatment tube .of about 50 to 200cubic feet per second which exhibits a Reynolds number preferably above about 4,000, and

Although the invention has been described with preapparent to those skilled in the art. Such variations and 13 1 l4 modifications are topbe considered within the purview 3 ln an apparatus for thermally processing continuand scope of the claims appended hereto. I v Y ous lengths ot' flbrous materials as defined in claim 2,

We claim: a, 'f' q r and 'wher eirithe improvement further comprises:

an apparatus for thermally processing continumeans cOnnectedt'o said aspirator means for introous lengths of fibrous materials .wherein said fibrousidl ll l ry l fltingflu id into said aspirator, materials-are passed thrpughga heating unit to takeuP and thereby'said heat treatment tube, from a meansisaid g unit. W ng; source" of heated fluid remote from said annular an elongatedcylmdncal heat treatment tube hav ng I end d mm P fil mP l P 4. in an apparatus for-thermally processing continusage therethrough of said fibrous materialsto be ous leng hs of tibfdb zas defined in claim 2 h fe Y '3 and whereinl'the improvement further comprises: W -"9,- I preheat means coaxially connected at an inlet end of n lia fl coaxlally unundmg 'said'aspirator means and being selectively operable said heat treatment tube for providing an annular receive-Maud fluid fromsaid annuar chamber chamber i t -Fa "eatmmt b? for introducing heated fluid into the inlet end of end closures being posltionedin the annular chamber said aspirator-means ahd forminimizing thc recap between i' Jack andsaid f 5 tion of relatively cooler ambient air into said aspiment tube closing the annular chamber at its ends;- means 7 v a means for introducing a fluid into said annular cham-' 7 be" p 5. in an apparatus for thermally processing continuan electric resistance heating coil mounted ivithin the h Highs-of fibrous manna defined-m clam -whe1 em said preheatmeans further comprises: interior Of Sald cylindrical acketforheatmg the fluid and'promoting the conductionof heat from k a the qganmy of said annular chamber through said heat treatment pi g g g filom said annular chamber tube to heat continuous lengths of fibrous materials m 0 l ea means passing thcnthmugh; 7 6 In an apparatus for thermally processing continumeans connectedto the inlet end of said heat treatousvkngths of flbrousmaterials defined m clam ment tube for introducing heated fluid from. said whcrem said heat recovery means compnses:

annular chamber into said heat treatment tube to r E 9i at the outlet end of thereby further heat said continuous lengths of tif, mat "F Fi and brous materials passing through said heat treathousmg iconcgnirfcany poslt'oned about said men! t b d porous tube and being in fluid communication with heat recovery means connected at the outlet end of dent fie a p reqceiving f q fluid said cylindrical heat treatment tube for receiving at p fl f fl P FQ Q tube f ddlvermg the least a portion of the heat passingthr'ough the outa ""F' hfatcd'fluld Said annular chamlet end of said cylindrical heat treatment tube and for delivering said heat into said annular chamber. ln'lan ppar f thermally Processing n in 2. In an apparatus for thermally processing continu- 95 83 0 55 3 IIQF S as defined i claim 6, ous lengths of fibrous materials as defined in'claim -l, Whetemsard heatreeovery means further comprises: said means for introducing the heated fluid into said 4 an annularrestnction connected-at the outlet end of heat treatment tube comprises: said porous tube to promote passage of heated fluid aspirator means coaxially mounted at the inlet end of r r from said cylindrical heat treatment tube through said heat treatment tube for receiving the heated said porous tube and into said housing means for fluid from said annular chamber and aspirating the delivery to said annular chamber. fluid into said heat treatment tube. 

1. In an apparatus for thermally processing continuous lengths of fibrous materials wherein said fibrous materials are passed through a heating unit to take-up means, said heating unit including, an elongated cylindrical heat treatment tube having an inlet end and outlet end for the continuous passage therethrough of said fibrous materials to be heat treated, wherein the improvement comprises: an elongated cylindrical jacket coaxially surrounding said heat treatment tube for providing an annular chamber about said heat treatment tube; end closures being positioned in the annular chamber between said cylindrical jacket and said heat treatment tube closing the annular chamber at its ends; means for introducing a fluid into said annular chamber; an electric resistance heating coil mounted within the interior of said cylindrical jacket for heating the fluid and promoting the conduction of heat from said annular chamber through said heat treatment tube to heat continuous lengths of fibrous materials passing therethrough; means connected to the inlet end of said heat treatment tube for introducing heated fluid from said annular chamber into said heat treatment tube to thereby further heat said continuous lengths of fibrous materials passing through said heat treatment tube; and heat recovery means connected at the outlet end of said cylindrical heat treatment tube for receiving at least a portion of the heat passing through the outlet end of said cylindrical heat treatment tube and for delivering said heat into said annular chamber.
 2. In an apparatus for thermally processing continuous lengths of fibrous materials as defined in claim 1, said means for introducing the heated fluid into said heat treatment tube comprises: aspirator means coaxially mounted at the inlet end of said heat treatment tube for receiving the heated fluid from said annular chamber and aspirating the fluid into said heat treatment tube.
 3. In an apparatus for thermally processing continuous lengths of fibrous materials as defined in claim 2, and wherein the improvement further comprises: means connected to said aspirator means for introducing auxiliary heating fluid into said aspirator, and thereby said heat treatment tube, from a source of heated fluid remote from said annular chamber.
 4. In an apparatus for thermally processing continuous lengths of fibrous materials as defined in claim 2, and wherein the improvement further comprises: preheat means coaxially connected at an inlet end of said aspirator means and being selectively operable to receive heated fluid from said annular chamber for introducing heated fluid into the inlet end of said aspirator means and for minimizing the reception of relatively cooler ambient air into said aspirator means.
 5. In an apparatus for thermally processing continuous lengths of fibrous materials as defined in claim 4, wherein said preheat means further comprises: means for selectively regulating the quantity of heated fluid introduced from said annular chamber into said preheat means.
 6. In an apparatus for thermally processing continuous lengths of fibrous materials as defined in claim 1, wherein said heat recovery means comprises: a porous tube coaxially mounted at the outlet end of said cylindrical heat treatment tube; and housing means concentrically positioned about said porous tube and being in fluid communication with said annular chamber for receiving heated fluid passing through said porous tube and delivering the thus received heated fluid into said annular chamber.
 7. In an apparatus for thermally processing continuous lengths of fibrous materials as defined in claim 6, wherein said heat recovery means further comprises: an annular restriction connected at the outlet end of said porous tube to promote passage of heated fluid from said cylindrical heat treatment tube through said porous tube and into said housing means for delivery to said annular chamber. 